Not Applicable
Not Applicable
Field of Invention
This invention pertains to a medium voltage motor controller. More particularly, this invention pertains to an integrated and compact design utilizing both cast components and compact components in a controller for electrical equipment.
A medium voltage controller for electrical equipment, such as motors, transformers, reactors, and capacitors, is provided. The controller is a one-high unit, that is, a single contactor in a full-height cabinet, with the contactor mounted near the base of the controller, the fuses and grounding switch located near the vertical center, the disconnect switch mounted above the fuses, and the controller""s instrument compartment located in the upper portion of the controller. The motor controller uses cast components to minimize components, fabrication steps, maintenance, and heat rise.
The motor controller is enclosed in an arc resistant cabinet, which uses the pressure generated by a fault to provide the sealing action to contain the fault forces. The rear, removable panels are inside the cabinet and engage lips surrounding the cabinet opening. Pressure inside the cabinet forces the panels against the inside surface of the cabinet and distributes the resulting load over a large area. The front access doors each have a continuous hinge and multiple latching tabs. The sheet metal panels of the cabinet are secured with a dimple-in-a-dimple feature, which provides strength and rigidity to the cabinet. At points where the panels are secured, each sheet metal part is formed with a dimple having a fastener hole in its center. The corresponding dimples in each sheet metal part are mated and fastened.
Another feature of the motor controller is the swaged connections, which are used for making internal electrical connections. A swaged connection includes a terminal or connector having a barrel, into which cable conductor is inserted. The portion of the barrel enclosing the cable conductor is compressed such that the cable conductor is cold-welded to the barrel.
The pull-out contactor has a withdrawable finger cluster formed of a one piece, self-aligning formed part that electrically mates with stabs inside the cabinet. The fingers are formed from conductive material that does not require additional springs to ensure proper electrical contact.
The controller""s instrument compartment is mounted in the upper portion of the controller. To aid in fabrication and maintenance, the instrument compartment includes a removable panel, which is modular and on which the instruments are wired and mounted. The instrument panel swings out of the controller to provide access to the main bus and line-side surge arrestors.
The contactor assembly is mounted on a truck and moves on a rail system that includes a pull-down handle with rails. The truck rolls out of the cabinet on the extended rails for easy removal from the cabinet. The truck, and contactor assembly, is racked in by pushing the truck into the cabinet and then raising the handle, which forces the draw-out fingers to engage the contact stabs.
A load discharge device (LDA) is included for grounding the load before the contactor can be removed from the controller. The LDA has a scissors-type closing mechanism, which, when actuated after being charged, causes a bar to contact each of the load conductors.
The fuses are mounted independently from the contactor assembly. The fuse spring clips are attached to a cast housing that provides corona protection and, in the case of the upper fuse clip housing, serves as the lower contact for the disconnect switch.
Each phase of the disconnect switch is formed of four conducting cast components. The cast upper switch contact includes a flat contact surface to which the main bus is connected. The cast lower switch contact includes the upper fuse clip housing. The cast configuration eliminates multiple connections, which are susceptible to high resistance and, consequently, heating. Electrical continuity between each of the two switch contacts is provided by two parallel plates that contact the two switch contacts by the disconnect switch operating mechanism. In the open position, the disconnect switch is earthed.
The disconnect switch has a window through which the equipment operator can view the position of the disconnect switch when the switch illuminator is actuated. An LED is positioned to shine light into the disconnect switch to illuminate the switch components. The LED is actuated by a manual switch and is powered by a portable power supply.
Low power current transformers are positioned near the load side of the contactor. The low power current transformer is a wide-range current transformer that provides amperage information to the protective metering devices from 0 amperes to 800 amperes, or more.
Internal temperature monitoring is performed by an optical temperature measuring system. Crystals are mounted on components that could experience elevated temperatures, such as the bus connections and the draw-out stabs. A pair of non-conductive fiber optic cables are connected between each crystal and a temperature sensor. The temperature sensor transmits an optical signal through a fiber optic cable and into the crystal. The signal excites the crystal and the temperature sensor receives the resulting fluorescence signal and determines the temperature of the crystal.